The present disclosure relates to a developing device, an image forming apparatus, and a developing device control method.
In general, in a developing device installed in an electrophotographic image forming apparatus, the thickness of a layer of developer formed on the surface of a developer carrying member is restricted by a layer thickness restricting portion. The layer thickness restricting portion is called a doctor blade or a restriction blade.
In some cases, the developer carrying member carries a two-component developer which contains toner and carrier. The developing device may include the developer carrying member and a toner carrying member, wherein the developer carrying member rotates while carrying the two-component developer, and the toner carrying member carries the toner supplied from the developer carrying member. In this case, the toner carrying member supplies the toner to an image carrying member on which an electrostatic latent image has been formed, such that the electrostatic latent image is developed by the toner. This developing method is called a touchdown developing or an interactive touchdown developing.
In the developing device, a large amount of toner and/or carrier separated from the developer carrying member may be deposited or adhered to the surface of the layer thickness restricting portion. The toner deposited on the layer thickness restricting portion is easy to move to the image carrying member, which may have an adverse effect on the image quality. In addition, if the developer containing the toner and/or the carrier adheres to the front-edge surface of the layer thickness restricting portion, the layer of the two-component developer formed on the outer circumferential surface of the developer carrying member becomes thinner. This results in a degradation of the image quality.
There is known a technology in which the developer carrying member carrying the two-component developer thereon is rotated in a direction reverse to a rotation direction of the developing, in order to remove the toner that has deposited on the layer thickness restricting portion. In this case, the magnetic brush of the two-component developer formed on the surface of the developer carrying member rubs off the toner deposited on the layer thickness restricting portion.